Differences Between Decennial Census and LAUS Data

The Census Bureau released Demographic Profile state and substate
data from the 2000 Census on a state-by-state basis between May 7
and June 4, 2002. These tabulations included data on socioeconomic
characteristics and labor force status for states, metropolitan
areas, counties, and smaller units of geography. The Census-based
labor force estimates may differ from the official labor force data
released by the Bureau of Labor Statistics (BLS) because of
differences in methodology, design, and data collection.

Background

Every ten years, the Bureau of the Census conducts a census of
the population. It is a snapshot of the population for one moment in
time (April 1 of the Census year). The main purpose of this Census
is to provide the population count needed for the re-apportionment
of seats in the House of Representatives and determination of State
legislative district boundaries.

The economic characteristics data from the 2000 Census are based
on a systematic sample of approximately 17 percent of the Census
households (i.e., every second, fourth, sixth, or eighth housing
unit, depending on the population of the area). The questions on the
long form address economic characteristics issues, including labor
force. This invites comparison with the official labor force data
from BLS that are developed by the Local Area Unemployment
Statistics (LAUS) program.

The Current Population Survey (CPS) has been the source of the
official estimates of unemployment for the nation for more than half
a century. The survey has been greatly expanded and improved over
the years, but the basic concepts of employment and
unemploymentreviewed periodically by high-ranking commissionshave
remained substantially unaltered. At present, the CPS is the sole
and official source of the monthly statistics on unemployment for
the nation. It is the main input to the estimating models that produce the
official monthly labor force estimates for all states, the District
of Columbia, New York City, and the Los Angeles-Long Beach-Glendale
metropolitan division. Through the LAUS methodology, the CPS also
affects estimates for nearly 7,200 substate areas.

Information on unemployment has been obtained in decennial
censuses since the late nineteenth century, although the current
concepts were not introduced until 1940, concurrent with the origins
of the CPS. There have always been differences in measured
unemployment between the CPS and the Census. Prior to 1990, however,
the Census-based estimates of the number unemployed had typically
been lower than those from the CPS, although the gap had generally
been closing over time. In 1950, the Census count of unemployed
persons for the nation was about 19 percent lower than the April
1950 figure from the CPS. The gap shrank to about 4 percent in 1960
and about 1.5 percent in 1970, before widening slightly, to about 3
percent (lower) in 1980. Census unemployment rates were below or
about the same as those from the CPS from 1950 to 1980. In 1990, for
the first time, the Census-based estimates of both the number of
unemployed and the unemployment rate were considerably higher than
the CPS figures, with the relative size of the gap being similar to
that obtained in 1950, but in the opposite direction.

Conceptual and methodological differences between the CPS and
Census

Interview-controlled environment versus self-enumeration

All data from the CPS are gathered by trained field
interviewers through personal visits and telephone interviews. For
the most part, decennial Census data are self-reported. That is,
individuals fill out a questionnaire by themselves. There are
generally no interviewers to clarify survey questions and probe
for more accurate and detailed responses, as is the case in the
CPS.

Specific versus general survey questions

The CPS currently uses 13 specific, detailed questions to
determine ones employment status. In the Census, the questions
are feweronly six. The enhanced specificity in the CPS is designed
to avoid misclassifications.

This is particularly relevant to the CPS active job search
concept, whereby respondents are probed to determine exactly what
active job hunting measures, if any, they have undertaken. Passive
activities, such as simply perusing classifieds, do not result in
a person being classified as unemployed in the CPS. However, given
the self-enumeration aspect of the Census, a person might count
such passive activities as looking for work.

Intensive versus limited quality control of data collection

CPS interviewers are trained extensively before going out into
the field, and proficiency checks are conducted regularly. In
addition, each month, a portion of the households in the sample
are reinterviewed, and the results are used to control and measure
the quality of the data. In the Census, the extent to which the
quality of the data can be controlled or evaluated is much more
limited.

Definite versus variable reference week

The CPS questions for determining current employment status
relate to a specific reference week, the week including the 12th
of the month (or, in the case of job search, the 4 weeks preceding
the survey week). The Census questions relate to the calendar week
preceding the date that the questionnaires were completed (in the
case of job search, the 4 weeks preceding the date of
reporting).

First interview reporting bias

In the CPS, households are in the sample for 4 consecutive
months, out of the sample for the following 8 months, and then
interviewed again for 4 months. There is a tendency among
households surveyed for the very first time (first month in
sample) and among those surveyed after the 8-month intermission
(fifth month in sample) to report higher levels of unemployment
than those who have been in the survey for several consecutive
months. This phenomenon affects one-fourth of the CPS sample. In
the Census, virtually every household is reporting for the first
time. Thus, any upward bias in unemployment associated with first
interview could conceivably affect the entire Census.

In addition to the above mentioned factors that not only
pertain to the 2000 Census, but also are relevant to several of
the prior Censuses, the 2000 Census was negatively impacted by a
data collection problem pertaining to group quarters, particularly
in towns with high percentages of college dormitory residents. In
particular, the form used to collect labor force status
information in group quarters (the Individual Census Report, or
ICR) was processed such that a very large number of incomplete
forms were systematically and erroneously allocated to
unemployment, resulting in implausibly high unemployment rates
being reported for these areas. While the Census Bureau has
acknowledged this problem and has undertaken some study of the
issue, no correction factors have been developed to produce more
accurate estimates for these areas.